Method for Producing an Optoelectronic Semiconductor Chip and Optoelectronic Semiconductor Chip

ABSTRACT

In an embodiment an electronic semiconductor chip includes a growth substrate with a growth surface including a flat region having a plurality of three-dimensionally designed surface structures on the flat region, a nucleation layer composed of oxygen-containing AlN in direct contact with the growth surface at the flat region and the three-dimensionally designed surface structures and a nitride-based semiconductor layer sequence on the nucleation layer, wherein the semiconductor layer sequence overlays the three-dimensionally designed surface structures, and wherein the oxygen content in the nucleation layer is greater than 1019 cm−3.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. application Ser. No.17/206,911, filed Mar. 19, 2021, entitled “Method for Producing anOptoelectronic Semiconductor Chip and Optoelectronic SemiconductorChip,” which is a continuation of U.S. application Ser. No. 16/384,550,filed Apr. 15, 2019, now U.S. Pat. No. 11,005,003, which is acontinuation of U.S. application Ser. No. 15/115,242, filed Jul. 28,2016, now U.S. Pat. No. 10,312,401, which is a national phase filingunder section 371 of PCT/EP2015/053051, filed Feb. 13, 2015, whichclaims the priority of the German patent application 10 2014 101 966.0,filed Feb. 17, 2014, each of which is incorporated herein by referencein its entirety.

TECHNICAL FIELD

A method for producing an electronic semiconductor chip and anelectronic semiconductor chip are provided.

SUMMARY

Embodiments of the invention provide a method for efficiently producingan electronic semiconductor chip. Further embodiments provide anelectronic semiconductor chip.

Pursuant to at least one embodiment of a method for producing anelectronic semiconductor chip, a growth substrate is provided. Saidgrowth substrate comprises a growth surface onto which semiconductorlayers are applied in the following steps. The growth surface is formedby a flat region on which a plurality of three-dimensional surfacestructures is designed. In other words, the growth surface comprises atwo dimensionally designed area, formed by the flat region, andthree-dimensionally designed areas, formed by the surface structures,which project from the plane formed by the flat region and/or projectfrom the latter into the growth substrate. The three-dimensional surfacestructures on the flat region of the growth surface also allow thesubstrate to be designated as pre-structured substrate.

For example, the surface structures can be formed by elevationsextending away from the flat region. Such elevations can more preferablybe conical, thus having a round cross-section when the growth surface isviewed from above, or pyramidal, thus having a polygonal cross-sectionwhen the growth surface is viewed from above, for example, a triangular,quadrangular, hexagonal or another polygonal cross-section.

Furthermore, the surface structures can also be formed by groovesprojecting into the growth substrate. Such grooves can, for example, beconical or pyramidal grooves, thus having a round cross-section or apolygonal cross-section when the growth surface is viewed from above,for example a triangular, quadrangular, hexagonal or another polygonalcross-section in the latter case.

Pursuant to a further embodiment, a nucleation layer is applied to thegrowth surface in a further step. Said nucleation layer is in particularintended to provide crystal surfaces onto which further layers, inparticular semiconductor layers, for example consisting of a nitridecompound semiconductor material of a high crystal quality, can beapplied. The nucleation layer thus provides surfaces on which a firstlayer of the semiconductor layer sequence can grow.

More preferably the nucleation layer is applied large-scale to thegrowth surface, meaning that the nucleation layer is not appliedselectively but instead onto both the flat region and thethree-dimensionally designed surface structures of the growth surface.The nucleation layer can also be formed by a plurality of posts arrangednext to each other, which are applied large-scale to the growth surface.“Large-scale” thus does not necessarily mean “all-over” in terms of thepresent application. A large-scale application is also achieved in termsof the present application when sections of the growth surface are notcovered by the nucleation layer, as long as at least sections of theflat region as well as sections of the surface structures are covered bythe nucleation layer.

The nucleation layer can be applied in such a way that, where possible,the entire growth surface, i.e. where possible, the entire flat regionand the surface structures, are covered by the nucleation layer. Thiscan, for example, ensue by way of a random-directional applicationprocess or by way of an application along a main direction that isperpendicular or substantially perpendicular to the flat region.Furthermore, it also possible to select a direction of applicationoriented obliquely to the flat region. Depending on the design of thesurface structures and the direction of application, this allows apartial shading of the flat region and/or the surface structures to beachieved, and therefore the nucleation layer may be applied to the flatregion and the surface structures, but only to a section of the flatregion and/or only to a section of the surface structures. Even in theevent of an application with shaded areas, the selectivity during growthof the semiconductor layer sequence described further below can still beachieved.

Pursuant to a further embodiment, a semiconductor layer sequence isgrown on the nucleation layer in a further step. Said semiconductorlayer sequence comprises at least one semiconductor layer and preferablya plurality of semiconductor layers. The semiconductor layer sequencecan in particular be grown by means of an epitaxy method, such as MOVPE(metal-organic vapor-phase epitaxy) or MBE (molecular beam epitaxy), andtherefore the growth substrate together with the nucleation layer thusform a so-called quasi substrate for the subsequent epitaxy.Furthermore, HVPE (hydride vapor phase epitaxy), LPE (liquid phaseepitaxy) or sputtering or combinations of the stated applicationprocesses for applying the semiconductor layer sequence are alsopossible.

The semiconductor layer sequence can in particular be a nitride-basedsemiconductor layer sequence. The designation “nitride-based” includesin particular semiconductor layers and semiconductor layer sequencescomprising a material from the III-V compound semiconductor materialsystem In_(x)Al_(y)Ga_(1-x-y)N with 0≤x≤1, 0≤y≤1 and x+y≤1, thus forexample GaN, AlN, AlGaN, InGaN, AlInGaN. The semiconductor layersequence can comprise dopants as well as additional components. For thesake of simplicity, however, only the essential components of thecrystal lattice, i.e. Al, Ga, In as well as N are stated, even if thelatter can be partially replaced and/or substituted by small quantitiesof further substances.

Pursuant to a further embodiment, the nucleation layer is formed byoxygen-containing aluminum nitride, hereinafter also designated as AlN:Oor AlON. The latter designations include compositions of the nucleationlayer in which the oxygen can be present as dopant or even in thepercent range in the nucleation layer. The oxygen content in thenucleation layer allows a special defect structure in the semiconductorlayer sequence to be achieved, which enables an efficient reduction inthe defect density or in an active layer of the semiconductor layersequence. The tensioning of the subsequently applied layers, i.e. of thesemiconductor layer sequence, can also be influenced. The oxygen canalso influence the degree of relaxation of the nucleation layer, whichcan substantially influence the curvature behavior of the subsequentlyapplied layers. In particular, oxygen-containing AlN can also influencethe selectivity with regard to the surface areas of the growth surfaceon which the semiconductor layer applied to the nucleation layer grows.

It has in particular been found that an epitaxial growth ofpre-structured substrates during the growth of the semiconductor layersequence on the nucleation layer requires a strong selectivity betweenthe two-dimensional flat region and the three-dimensionally designedsurface structures arranged thereupon, in particular the facets of thesurface structures designed as elevations or grooves, in order toproduce a semiconductor layer sequence of sufficient quality. In otherwords, specific surface areas of the growth surface need to be selectedon which a growth of a semiconductor layer on the nucleation layerensues, while no or only little growth preferably ensues on othersurface areas. In particular, a targeted selection needs to be madebetween the flat region and surfaces of the three-dimensionally designedsurface structures as possible growth surfaces for an epitaxiallyapplied semiconductor material. If such a selectivity is non-existent,the result is a poor material quality and a yield weakening, inparticular in the event of a semiconductor chip designed as alight-emitting diode with regard to the low current behavior and theblock voltage as well as with respect to a poorer performance, such as alower light output, for instance. Furthermore, in the event ofsemiconductor chip designed as a light-emitting diode, the light outputfrom the semiconductor chip benefitting from the surface structures onthe growth surface can be negatively influenced by the non-existentselectivity. The amount of emitted light can also be reduced byabsorption in parasitic, crystalline very poor GaN areas.

In order to achieve as good a selectivity as possible in pre-structuredsubstrates between the three-dimensional surface structures and thesmooth surface areas located therebetween of the flat region of thegrowth surface, attempts were made in the past to adjust special processconditions during nucleation, for example an increased pressure and avery low ratio of the group V elements to the group III elements in theevent of a GaN nucleation. Despite such measures, a significant epitaxyfor the further epitaxy nevertheless took place on the three-dimensionalstructures in prior art. In addition, the process windows are generallyseverely constrained and require constant time-consuming control.

The nucleation layer consisting of oxygen-containing aluminum nitrideallows the semiconductor layer sequence to be selectively grown from theflat region of the growth surface, meaning that the growth of thesemiconductor layer sequence or of a first layer or of a first layerarea of the latter ensues selectively on the flat region, i.e. that aformation of the semiconductor layer sequence begins selectively on theflat region. This can in particular mean that a large proportion of thegrowth of the semiconductor layer sequence ensues from the flat regionand a small proportion thereof from the surfaces of thethree-dimensionally designed surface structures. The semiconductor layersequence in an epitaxial variant preferably grows only substantiallyfrom the flat region, whereas very little or even no growth at all ofthe semiconductor layer sequence takes place on the surface structures.This ensures that the three-dimensionally designed surface structuresare not overgrown by the semiconductor layer sequence, i.e. the latterdoes not grow directly on said surface structures and, instead, thethree-dimensionally designed surface structures are substantiallycovered by the semiconductor layer sequence, said semiconductor layersequence thus covering the surface structures by the growth from theflat region. “Substantially” in this context means that no growth of thesemiconductor layer sequence or only a small proportion thereof evertakes place on the surface structures.

Pursuant to a further embodiment, the selectivity of the growth of thesemiconductor layer sequence on the flat region is preferably targetedlyadjusted by means of the oxygen content of the nucleation layer.Whereas, in the event of an oxygen-free AlN nucleation layer, the growthof the semiconductor layer sequence on the surfaces of thethree-dimensionally designed surface structure has been found to bedominant compared with the growth on the flat region, increasing theoxygen content of the nucleation layer can achieve the previouslydescribed advantageous selectivity. AlN with an oxygen content of lessthan 10¹⁹ cm⁻³ can be designated as oxygen-free AlN herein.

Pursuant to a further embodiment, the application of the nucleationlayer ensues by means of metal-organic vapor-phase epitaxy. Theselection of suitable starting materials, also designated as precursors,and the gaseous flux thereof allows the nucleation layer to be producedwith any desired oxygen content. O₂, H₂O, nitric oxide or anyoxygen-containing metal-organic compound can be used as a source ofoxygen. A gas source based on N₂ and/or H₂, mixed with O₂ and/or nitricoxides can be used, for example. H₂O to which a carrier gas is added viaa bubbler can also be used. Another possibility, for example, is that ametal-organic gas source containing oxygen is used, for examplediethylaluminum ethoxide or a mixture of diethylaluminum ethoxide andtrimethylaluminum. The control of the amount of oxygen-containing gasesadded during the growth process of the nucleation layer allows theoxygen concentration of the nucleation layer to be controlled andtargetely adjusted.

Furthermore, another possibility is to terminate the growth surface withoxygen. For example, the growth substrate can be pre-conditioned in O₂plasma to this end. Such an oxygen termination of the growth surfaceleads to the growth of oxygen-containing AlN with gas sources as well,which are usually used for producing oxygen-free AlN nucleation layers.In particular, an aluminum oxide growth substrate can be preconditionedby an O₂ plasma, as the oxygen termination of the aluminum surface canlead to growth of oxygen-containing AlN specifically on the aluminumoxide-aluminum nitride limiting surface.

The previously described sources or methods for providing the oxygen canalso be combined with each other, for example a surface conditioningwith oxygen and the addition of an oxygen-containing gas.

Pursuant to a further embodiment, the application of the nucleationlayer ensues by means of sputtering. To this end, for example, an Altarget can be used in a nitrogen atmosphere, to which oxygen is added.In contrast to metal-organic vapor-phase epitaxy, sputtering also allowsthick layers to be generated comparatively cost-effectively and withrelatively high growth rates. The generation of the nucleation layer bymeans of sputtering also allows the subsequent epitaxial process forgrowing the semiconductor layer sequence to be shortened and/orsimplified. Furthermore, the sputtering of the nucleation layer allowsthe presence of aluminum to be reduced in a subsequent MOVPE process forgenerating the semiconductor layer sequence.

Furthermore, other methods for applying the nucleation layer are alsopossible, for example MBE, CVD (chemical vapor deposition) or a suitablephysical method.

Pursuant to a further embodiment, the amount of oxygen in the nucleationlayer is controlled in such a way that the oxygen content in thenucleation layer equals more than 10¹⁹ cm⁻³. In particular, the weightproportion of the oxygen on the nucleation layer can preferably begreater than or equal to 0.01%, greater than or equal to 0.1%, greaterthan or equal to 0.2% or greater or equal to 0.5%. Furthermore, theweight proportion of the oxygen on the nucleation layer can preferablybe less than or equal to 10%, less than or equal to 5% or less than orequal to 1.5%.

Furthermore, another possibility is to apply a layer of oxygen-free AlNwith one of the aforementioned methods, subsequently oxide it in anoxidation oven and thus convert it into an oxygen-containing AlN layer.

Pursuant to a further embodiment, the nucleation layer is applied to thegrowth surface with a thickness of greater than or equal to 1 nm,greater than or equal to 5 nm, greater than or equal to 10 nm, greaterthan or equal to 30 nm or greater than or equal to 50 nm. Alternativelyor additionally, the thickness of the nucleation layer can be less thanor equal to 1000 nm, less than or equal to 200 nm or less than or equalto 150 nm. For example, the thickness of the nucleation layer can beapproximately 100 nm.

Pursuant to a further embodiment, the growth substrate comprises orconsists of aluminum oxide Al₂O₃. In particular, as flat region of thegrowth surface in such case, the growth substrate can comprise acrystallographic c surface with 0001 orientation or (−c) surface with000-1 orientation of the aluminum oxide. In particular, it has beenfound that an oxygen-containing AlN nucleation layer allows the growthof the semiconductor layer sequence on the aluminum oxide c surface oraluminum oxide (−c) surface to be selectively selected, whereas no oronly little growth of the semiconductor layer sequence on the nucleationlayer ensues on the crystal surfaces providing the three-dimensionallydesigned surface structures and in such case being different to the csurface or (−c) surface and containing a multiplicity of crystalsurfaces.

Furthermore, another possibility is that the flat region is formed by anr surface of aluminum oxide, which is particularly suitable for growingsemipolar gallium nitride.

Furthermore, the growth substrate can also comprise a silicon-containinggrowth surface. In particular, the growth surface can be formed by asilicon surface or a silicon carbide surface. To this end, the growthsubstrate can, for example, be a silicon substrate or a SiC substrate orcomprise a silicon or SiC layer on another substrate. In addition, thegrowth substrate can also comprise or consist of one of the followingmaterials: LiGaO, LiAlO, ZnO, quartz glass, mica.

Pursuant to at least one embodiment, a semiconductor layer sequence isgrown via the nucleation layer with an optoelectronic active layer. Saidoptoelectronic active layer of the semiconductor layer sequence can beset up and provided during operation of the semiconductor chip foremitting and/or for detecting light, in particular in the ultraviolet orin the visible spectral range. In particular, a wavelength of thegenerated or detectable light can equal between 380 nm and 680 nminclusively. The optoelectronic active layer can preferably comprise oneor more pn transitions or one or more quantum well structures. Thesemiconductor chip can thus be designed as light-emitting diode or aslight-detecting diode.

The semiconductor layer sequence can also comprise at least one or moren doped layers and at least one or more p doped layers, wherein each ofthese doped semiconductor layers can preferably be directly adjacent tothe optoelectronic active layer. In addition, the semiconductor layersequence can, for example, also comprise undoped layers, such as abuffer layer, for instance. The latter can, for example, be directlygrown on the nucleation layer and have a thickness, which is greaterthan the height of the three-dimensionally designed surface structures,and therefore the surface structures can be covered by means of thebuffer layer.

Pursuant to a further embodiment, an electronic semiconductor layercomprises a growth substrate with a growth layer, which is formed by aflat region with a plurality of three-dimensionally designed surfacestructures on the flat region. Furthermore, the semiconductor chip cancomprise a nucleation layer composed of AlN:O directly appliedlarge-scale to the growth surface and a nitride-based semiconductorlayer sequence on the nucleation layers, wherein the semiconductor layersequence is selectively grown from the flat region.

The embodiments and features described in conjunction with the methodfor producing the electronic semiconductor chip apply equally to thesemiconductor chip and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, advantageous embodiments and developments resultfrom the embodiments described below in conjunction with theillustrations.

Shown in:

FIGS. 1a to 5 are schematic diagrams of steps in a method for producingan electronic semiconductor chip,

FIGS. 6a to 6c are secondary electron microscope images of the growth ofGaN on nucleation layers pursuant to further embodiments and

FIG. 7 are measurements of wafer bows during the semiconductor growthwhen using different nucleation layer compositions.

Identical, similar or seemingly identical elements in the embodimentsand illustrations can always be furnished with the same reference signs.The elements shown and the size ratios amongst each other should not beviewed as true-to-scale; instead individual elements, such as layers,components, structural units and areas, can be shown exaggeratedly largefor the sake of better representation and/or better understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIGS. 1A to 5 shows steps in a method for producing an electronicsemiconductor chip 100. Said electronic semiconductor chip 100 is purelyexemplarily designed as a light-emitting diode with an optoelectronicactive layer, which is set up for generating and emitting light duringoperation. As an alternative to a light-emitting diode, the electronicsemiconductor chip 100 can, for example, also be designed as alight-detecting diode or as another semiconductor element, for exampleas transistor, or comprise such an element.

In a first step a growth substrate 1 is provided that, as shown in FIG.1A, comprises a growth surface 10. Said growth surface 10 is providedfor the purpose of growing a semiconductor layer sequence on this onesemiconductor layer sequence. The growth substrate 1 in the embodimentshown comprises aluminum oxide (Al₂O₃) and is preferably composed ofaluminum oxide. In particular, the growth substrate 1 can be designed asaluminum oxide wafer, on which a semiconductor layer sequence is grownlarge-scale. The separation of the wafer with the grown semiconductorlayer sequence allows a plurality of semiconductor chips to be produced.

The growth surface 10 comprises a two-dimensionally designed flat region11, on which a plurality of three-dimensionally designed surfacestructures 12 is arranged. In other words, the surface structures 12project out of the plane formed by the flat region 11. Thethree-dimensionally designed surface structures 12 are designed aselevations, which extend upwards away from the flat region 11.

FIGS. 1B and 1C show views of the growth surface 10 from growthsubstrates 1, in which the cross-section of the surface structures 12 isrecognizable. As shown in FIG. 1B, the cross-section of the surfacestructures 12 can be round and in particular circular, and therefore thesurface structures 12 can be designed as conical elevations.Alternatively, the surface structures 12 can also comprise an angular,for example a hexagonal cross-section, as shown in FIG. 1C, andtherefore the surface structures 12 can also be designed as pyramidalelevations on the flat region 11, said flat region 11 extends betweenthe surface structures 12 designed as elevations.

The flat region 11 is more preferably formed by a crystallographic csurface or (−c) surface of the aluminum oxide, which is particularlysuitable for growing nitride-based semiconductor materials. Accordingly,the surfaces of the surface structures 12 are formed by a plurality ofother crystal surfaces in compliance with their orientation relative tothe flat region 11.

Alternatively to the embodiment shown, the growth substrate 1 can, forexample, also comprise a growth surface 10 formed by silicon or siliconcarbide and be correspondingly designed, for example, as silicon waferor silicon carbide wafer. Furthermore, another possibility is that thegrowth substrate comprises or consists of another material stated abovein the general section above.

FIG. 1D shows an alternative embodiment for the growth substrate 1, inwhich the surface structures 12 are designed in contrast to theembodiment in FIG. 1a as grooves projecting from the flat region 11 intothe growth substrate 1. Similarly to the previously describedelevations, the grooves can, for example, be conical or pyramidal. Thefollowing description of the further steps refers purely exemplarily tothe embodiment of the growth substrate 1 pursuant to FIG. 1 withelevations as surface structures, but the growth substrate in the stepsdescribed in the following can also be provided with grooves as surfacestructures 12.

In a further step, as shown in FIG. 2, a nucleation layer 2 is appliedto the growth surface 10. In particular, said nucleation layer 2 isapplied large-scale, i.e. on the flat region 11 as well as on thethree-dimensionally designed surface structures 12 of the growth surface10. The nucleation layer 2 consists of oxygen-containing aluminumnitride, i.e. AlN:O or AlON, which is applied directly to the growthsurface 10.

For example, a metal-organic vapor-phase epitaxy (MOVPE) can be used tothis end, in which an oxygen-containing starting material is used inaddition to suitable starting materials for providing Al and N, asdescribed in the general section. Alternatively or additionally, asdescribed in the general section, an oxygen termination of the growthsurface 10 can be implemented.

As an alternative to an MOVPE method, the nucleation layer 2 can also beapplied by means of a sputtering method. As described in the generalsection, an Al target in a nitrogen atmosphere that also additionallycontains oxygen can, for example, be used to this end. Furthermore,another method described in the general section above is also possible.

The amount of oxygen in the nucleation layer 2 is controlled in such away that the oxygen content in the nucleation layer 2 equals more than10¹⁹ cm⁻³. In particular, the weight proportion of the oxygen on thenucleation layer 2 can preferably be greater than or equal to 0.01%,greater than or equal to 0.1%, greater than or equal to 0.2% or greateror equal to 0.5%. Furthermore, the weight proportion of the oxygen onthe nucleation layer can preferably be less than or equal to 10%, lessthan or equal to 5% or less than or equal to 1.5%.

The thickness of the nucleation layer 2 is greater than or equal to 1nm, greater than or equal to 5 nm, greater than or equal to 10 nm,greater than or equal to 30 nm or greater than or equal to 50 nm.Furthermore, the nucleation layer 2 can be produced with a thickness ofless than or equal to 1000 nm, less than or equal to 200 nm or less thanor equal to 150 nm. For example, the thickness of the nucleation layercan be approximately 100 nm.

In a further step described in conjunction with FIGS. 3 to 5, anitride-based semiconductor layer sequence is grown on the nucleationlayer by means of MOVPE.

As shown in FIG. 3, the growth of the semiconductor layer ensuesselectively from the flat region 11. As described in the generalsection, this is possible due to the fact that the nucleation layer 2 isnot composed of AlN, as is usual in prior art, but instead additionallycontains oxygen. The oxygen content of the nucleation layer 2 allows theselectivity of the growth of the semiconductor layer sequence to beadjusted on the flat region 11, and therefore the semiconductor materialto be grown is predominantly grown from the flat region 11 to thenucleation layer 2 due to the desired selectivity. Conversely, little orno growth occurs on the surfaces of the three-dimensionally designedsurface structures 12 due to the use of the oxygen-containing AlNnucleation layer 2, as can be seen in FIG. 3 in which an initial stageof the growth process for producing the semiconductor layer sequence 3can be seen: a semiconductor material 30, which is applied for producinga first semiconductor layer 31 of the semiconductor layer sequence 3,grows selectively upwards from the flat region 11 on the nucleationlayer 2.

FIGS. 6A and 6B show secondary electron microscope images of acorresponding stage in the method when growing GaN on anoxygen-containing AlN nucleation layer. The images correspond to a viewfrom above of the growth surface according to the view in FIG. 1C. Inthe event of the image in FIG. 6a , the nucleation layer was applied bymeans of MOVPE using an oxygen-containing starting material, whereas, inthe event of the image in FIG. 6, the nucleation layer was sputtered onby adding oxygen. In both images it is very clearly recognizable thatthe surface structures 12 show only little or no growth whatsoever ofthe semiconductor material 30 and that the latter instead growsselectively between the surface structures 12 and thus on the flatregion of the growth surface.

In comparison to this, the growth on a corresponding growth substratewhen using an oxygen-free AlN nucleation layer is shown. As is easilyrecognizable, the growth here ensues more intensively on the surfaces ofthe surface structures, which are covered by the semiconductor material30 and are thus unrecognizable in the image. As a result, the grownsemiconductor material 30 forms no uniform crystal surface, but insteadcomprises a plurality of crystal surfaces, which leads to a poormaterial quality of the further grown semiconductor material or insubsequently grown semiconductor layer sequence.

The addition of oxygen during the production of the nucleation layer 2thus allows a strong selectivity of the subsequent growth process of thesemiconductor material of the semiconductor layer sequence to beachieved both when using an MOVPE method and when using a sputteringmethod for producing the nucleation layer. The addition of oxygen canthus ensue both within an MOVPE method during the correspondingproduction of the nucleation layer 2 and outside said method during theproduction of the nucleation layer by means of sputtering. Conversely,alternative nucleation processes with oxygen-free AlN within MOVPEmethods always lead to significant parasitic nucleations on the surfacestructures, as shown in FIG. 6C.

As shown in FIG. 4, the semiconductor material grown on the nucleationlayer 2 can be grown so far that a semiconductor layer 31 forms, forexample an undoped buffer layer, which then covers the surfacestructures 12. As an alternative, the semiconductor layer 31 can alsocomprise a plurality of layers with differing undoped and/or dopedmaterials.

In order to form the semiconductor layer sequence 3, furthersemiconductor layers are then grown on the semiconductor layer 31. Asshown in FIG. 5, said further semiconductor layers can, for example, beformed by doped semiconductor layers 32, 33, between which anoptoelectronic active layer 34 is arranged. The semiconductor layersequence 3 can, in particular, consist of a plurality of doped andundoped layers, which are not shown here for the sake of clarity. Inparticular, the structure of a semiconductor layer sequence 3 for alight-emitting or light-detecting diode is known to a person skilled inthe art and is thus not further elaborated. The semiconductor chip 100shown in FIG. 5 can additionally comprise further layers, such aselectrode layers for electrically contacting the semiconductor layersequence, mirror layers and/or passivation layers, for example, whichare likewise not shown for the sake of clarity.

In the exemplary embodiment of the electronic semiconductor chip 100 aslight-emitting diode, the semiconductor chip 100 can emit light in thedirection of an upper side facing away from the growth substrate 1 aswell as in the direction of the growth substrate 1 during operation. Adecrease or reduction in total reflection can be achieved by the surfacestructures 12 for light emitted by the optoelectronic active layer 34 inthe direction of the growth substrate 1.

The previously described method allows an improvement in the selectivityof the growth process of the semiconductor layer sequence on thenucleation layer to be achieved by the use of an oxygen-containing AlNnucleation layer on a pre-structured substrate, which can alsoadvantageously lead to a significant expansion of the process parametersof the subsequent layers. Furthermore, the low and preferably scant ornon-existent growth of the three-dimensionally designed surfacestructures positively influences not only the material quality in theevent of light-emitting diodes but also the electroscopic parameters,such as light, leakage currents and low current behavior, for example.As no time-consuming temperature ramps and pressure slopes are necessaryduring the nucleation, it may be possible to perceptibly reduce thegrowth time in an MOVPE system.

In addition, it has been found that a determination of the degree ofrelaxation of the deposited oxygen-containing aluminum nitride asnucleation layer and the monitoring degree of the three-dimensionallydesigned surface structures allows an adjustment of the curvature of thegrowth substrate during the growth of semiconductor layer sequence. Tothis end, FIG. 7 shows wafer bows C during the semiconductor growingprocess in accordance with the processing time t for differentcompositions of the nucleation layer. It has been found that thecurvature of the wafers during growth can be controlled by thecharacteristics of the oxygen-containing AlN nucleation layer. Thetargeted addition and amount of oxygen can influence the degree ofrelaxation of the oxygen-containing AlN and, accordingly, the state oftensioning of the subsequent layers.

The embodiments shown in the illustrations can comprise further andalternative features pursuant to the description in the general section.

The description on the basis of the embodiments does not restrict theinvention thereto. Instead, the invention includes every new feature aswell as every combination of features, which in particular includes verycombination of features in the claims, even if such feature or suchclaim is not itself explicitly stated in the claims or embodiments.

What is claimed is:
 1. An electronic semiconductor chip comprising: agrowth substrate with a growth surface comprising a flat region having aplurality of three-dimensionally designed surface structures on the flatregion; a nucleation layer composed of oxygen-containing AlN in directcontact with the growth surface at the flat region and thethree-dimensionally designed surface structures; and a nitride-basedsemiconductor layer sequence on the nucleation layer, wherein thesemiconductor layer sequence overlays the three-dimensionally designedsurface structures, and wherein an oxygen content in the nucleationlayer is greater than 10¹⁹ cm⁻³.
 2. The electronic semiconductor chipaccording to claim 1, wherein the nucleation layer is a sputterd layer.3. The electronic semiconductor chip according to claim 1, wherein thethree-dimensionally designed surface structures are conical or pyramidalelevations on the flat region.
 4. The electronic semiconductor chipaccording to claim 1, wherein the growth substrate comprises aluminumoxide.
 5. The electronic semiconductor chip according to claim 4,wherein the flat region is a crystallographic c surface.
 6. Theelectronic semiconductor chip according to claim 1, wherein the growthsubstrate consists of aluminum oxide.
 7. The electronic semiconductorchip according to claim 1, wherein the semiconductor layer sequencecomprises an optoelectronic active layer configured to emit or detectlight.
 8. The electronic semiconductor chip according to claim 1,wherein the semiconductor chip is a light-emitting or light-detectingdiode.
 9. The electronic semiconductor chip according to claim 1,wherein the nucleation layer is formed by a plurality of posts arrangednext to each other which are applied large-scale to the growth surface.10. The electronic semiconductor chip according to claim 1, wherein thesemiconductor layer sequence is not grown onto the three-dimensionallydesigned surface structures.
 11. A method for producing an electronicsemiconductor chip, the method comprising: providing a growth substratewith a growth surface comprising a flat region having a plurality ofthree-dimensionally designed surface structures on the flat region;applying a nucleation layer composed of oxygen-containing AlN directlyto the growth surface onto the flat region and the three-dimensionallydesigned surface structures, wherein an oxygen content in the nucleationlayer is greater than 10¹⁹ cm⁻³; and growing a nitride-basedsemiconductor layer sequence on the nucleation layer, wherein thesemiconductor layer sequence overlays the three-dimensionally designedsurface structures, and wherein growing the semiconductor layer sequencebegins selectively on the flat region.
 12. The method according to claim11, wherein the nucleation layer is sputterd.
 13. The method accordingto claim 11, wherein the three-dimensionally designed surface structurescomprise conical or pyramidal elevations on the flat region.
 14. Themethod according to claim 11, wherein the growth substrate comprisesaluminum oxide.
 15. The method according to claim 14, wherein the flatregion is a crystallographic c surface.
 16. The method according toclaim 11, wherein the growth substrate consists of aluminum oxide. 17.The method according to claim 11, wherein the semiconductor layersequence comprises an optoelectronic active layer for emitting ordetecting light.
 18. The method according to claim 11, wherein thenucleation layer is formed by a plurality of posts arranged next to eachother which are applied large-scale to the growth surface.